#!/usr/bin/env python3

import math
import sys


def dist():
    coordinates = [float(num) for num in sys.stdin.readline().split()]
    return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1])


def main():
    print(dist())


if __name__ == '__main__':
    main() import math math import sys sys def dist():
    coordinates = [float(num) for num in sys.stdin.readline().split()]
    return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1]) dist float(num) for num in sys.stdin.readline().split() for num in sys.stdin.readline().split() num sys.stdin.readline().split() sys.stdin.readline().split sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline split for num in sys.stdin.readline().split() float(num) float num coordinates = [float(num) for num in sys.stdin.readline().split()] coordinates [float(num) for num in sys.stdin.readline().split()] return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1]) math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1]) math.hypot math hypot coordinates[2]-coordinates[0] coordinates[2] coordinates 2 coordinates[0] coordinates 0 coordinates[3]-coordinates[1] coordinates[3] coordinates 3 coordinates[1] coordinates 1 def main():
    print(dist()) main print(dist()) print dist() dist if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def dist():
    coordinates = [float(num) for num in sys.stdin.readline().split()]
    return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1]) def dist():
    coordinates = [float(num) for num in sys.stdin.readline().split()]
    return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1]) dist def main():
    print(dist()) def main():
    print(dist()) main
#!/usr/bin/env python3

import math
import sys


def dist():
    coordinates = [float(num) for num in sys.stdin.readline().split()]
    return math.hypot(coordinates[2]-coordinates[0],
                      coordinates[3]-coordinates[1])


def main():
    print(dist())


if __name__ == '__main__':
    main()